Effects of Mahuang decoction on hippocampal amino acid neural transmitter release in rats evaluated by microdialysis / 中国药理学通报

ABSTRACT

Aim Toinvestigatetheeffectofhigh,me-dium and low doses of Mahuang decoction on the re-lease amount of rat hippocampal neural transmitter (Glu,Gly,Asp,GABA),then compare Mahuang de-contion with ephedra alkaloids and ephedra.Methods Ratswererandomlydividedinto6groupsandgiven orally with Mahuang decoction of high dose (calculated by ephedra 4 g·kg-1 ),medium dose (calculated by ephedra 2 g·kg-1 ),low dose (calculated by ephedra 1 g · kg-1 ),ephedra (calculated by ephedra 2 g · kg-1 ),ephedra alkaloids (ephedrine 7 mg · kg-1 , pseudoephedrine 2. 4 mg · kg-1 , methylephedrine 1. 12 mg · kg-1 )and blank control group.Samples were obtained from the hippocampus of conscious rat by microdialysis sampling technique.The content of ami-no acid neurotransmitters in dialysates was detected u-sing the established HPLC-ECD with OPA pre-column derivationmethod.Results Fouraminoacidneuro-transmitters could be well separated in 28 min.High, medium and low doses of Mahuang decoction,ephedra and ephedra alkaloids significantly increased the con-tent of these four amino acid neurotransmitters,com-pared with blank control group (P<0. 05 ).Ephedra alkaloids significantly reduced the levels of inhibitoryamino acid neurotransmitters GABA and Gly in 90 min,compared with the medium dose of Mahuang de-coction.Excitatory neurotransmitters of ASP and Glu in hippocampus showed the trend of increase first and then decrease after oral administration of Mahuang de-coction and ephedra. The levels of Glu and Asp reached peaks from 90 min to 120 min after treatment with Mahuang decoction,and also increased along with dose increase of Mahuang decoction.In comparison with the medium dose of Mahuang decoction group,the level of Glu reached peak at 90 min and 150 min in ephedra alkaloids group and ephedra group respective-ly,and the content of Glu significantly increased at peaktime.Conclusions Increasedcontentofexcita-tory amino acid neurotransmitters (Asp and Glu ) shows positive correlation with the dose of Mahuang de-coction.Other components in Mahuang decoction in-hibits the up-regulation effect of ephedra and ephedra alkaloids on Glu,and promotes the up-regulation effect of ephedra alkaloids on GABA and Gly.